Spatial light modulators are widely used in commercial products such as video displays, televisions, and the like. In general, a spatial light modulator includes an array of cells, each of which includes a micro mirror that can be tilted about an axis and, furthermore, circuitry for generating electrostatic forces that operate to tilt the micro mirror. In addition, a spatial light modulator cell typically includes structures that hold and allow the tilting of the micro mirror. There are gaps between the cells for accommodating such structures. Each cell of a spatial light modulator usually further includes stoppers for mechanically stopping the cell's micro mirror at the “on” position and the “off” position, respectively.
In one implementation, for example, in a digital mode of operation for displaying video images, there are two positions at which the micro mirror can be tilted. In an “on” position or state, the micro mirror directs incident light to an assigned pixel of a display. In an “off” position or state, the micro mirror directs incident light away from the assigned pixel. The “on” position can be, for example, 20 degrees from the horizontal position, and the “off” position can be, for example, 15 degrees from the horizontal position.
Spatial light modulators implemented as described above generally operate by tilting a selected combination of micro mirrors to selectively project light to display an image on the display. FIG. 1 schematically illustrates a spatial light modulator formed on substrate 2. The spatial light modulator includes metal post 6, and micro mirror 8 residing on metal post 6. Micro mirror 8 may be tilted (as shown using dashed lines) when voltages are applied on metal electrodes 4. Light thus may be reflected by micro mirror 8 to, or away from, the display (not shown).
The conventional spatial light modulator as shown in FIG. 1 suffers from drawbacks. First, the height H of metal post 6 is typically great according to the standards of integrated circuit formation processes, and the depositing and patterning of metal post 6 is relatively difficult. Second, due to the requirements that metal posts/electrodes 6 and 4 have different heights, various lithography processes are needed to precisely control the heights of the metal posts/electrodes 6 and 4, again causing an increase in the manufacturing cost. New methods for forming metal posts 6 are thus needed.